BACKGROUND: There has been a dramatic escalation in sugar intake in the last few
decades, most strikingly observed in the adolescent population. Sugar
overconsumption has been associated with several adverse health consequences,
including obesity and diabetes. Very little is known, however, about the impact
of sugar overconsumption on mental health in general, and on reward-related
behavioral disorders in particular. This study examined in rats the effects of
unlimited access to sucrose during adolescence on the motivation for natural and
pharmacological rewards in adulthood.
METHODOLOGY/PRINCIPAL FINDINGS: Adolescent rats had free access to 5% sucrose or
water from postnatal day 30 to 46. The control group had access to water only. In
adulthood, rats were tested for self-administration of saccharin (sweet),
maltodextrin (non-sweet), and cocaine (a potent drug of abuse) using fixed- and
progressive-ratio schedules, and a concentration-response curve for each
substance. Adult rats, exposed or not exposed to sucrose, were tested for
saccharin self-administration later in life to verify the specificity of
adolescence for the sugar effects. Sugar overconsumption during adolescence, but
not during adulthood, reduced the subsequent motivation for saccharin and
maltodextrin, but not cocaine. This selective decrease in motivation is more
likely due to changes in brain reward processing than changes in gustatory
perception.
CONCLUSIONS/SIGNIFICANCE: Sugar overconsumption induces a developmental
stage-specific chronic depression in reward processing that may contribute to an
increase in the vulnerability to reward-related psychiatric disorders.